Underreamer



Sept. 8, 1931. E. s. HARTSON UNDERREAMER Filed Feb. 26, 1927 v1 vr0 1e, Jez;Z 27W @Q? ll llnl'.

Patented Sept. 8, 1931 PATENT OFFICE EARL S. HAB'ISON, OF LOS ANGELES, CALIFORNIA UNDERREAMER Application filed February 26, 1927. Serial No. 171,212.

My invention relates to an underreamer that is particularly designed for use in oil wells for reaming or enlarging that portion of the drill hole that is below the casing in order that the latter may be lowered into the well hole as the drilling and underreaming operations proceed.

The principalobjects of my invention are to generally improve upon and simplify the 1 construction of the existing forms of underreamers; to provide relatively simple and efficient means for effecting a positive outward or expanding movement to the bits or cutter blades and likewise, for positively retracting or drawing said bits or cutter blades into the shell or housing; to provide strong, rigid and substantial hearings on the housing for the bits or cutter blades in order that the latter will, through their connection with the housing, effectually withstand the strains and stresses to which they may be subjected while in service; to provide in an underreamer of the character referred to, a tubular threaded mandrel that forms a part of the drill tube and which mandrel is effective in imparting vertical movement to the conical member that imparts positive expanding and contracting movements to the bits or cutter blades; further, to provide relatively simple, strong and substantial bearin s between the end portions of the housing 0 the underreamer and the tubular threaded mandrel; and further, to provide improved bearings between the ends of the vertically movable cone and the ends of the housing so as to effectually prevent any tendency of the parts to freeze when the ends of the conical member are brought into engagement with the bearings at the ends of d: the housing.

With the foregoing and other ob ects in view, my invention consists in certain novel features of construction and arrangement of parts that will hereinafter be more fully described and claimed and-illustrated in the accompanying drawings, in which Fig. 1 is a vertical section taken lengthwise through the center of an underreamer embodying the principles of my invention and showing the bits or cutter blades in their fully expanded positions.

.seated on the ends of this shell are rounded Fig. 2 is a horizontal section taken on the hue 22 of Fig. 1. Fig. 3 is an elevational view of the medial portion of the housing of the underreamer and showing one of'the bits or cutter blades. Referring by numerals to the accompany- 1ng drawings, which illustrates a practical embodiment of my invention, 10 designates a hollow cylindrical shell that forms the body of the housing of the underreamer and screwcaps or heads 11. Each cap is provided with a centrally arranged opening in which 1s seated a bushing 12, preferably of bronze, and formed on the inner face of each bushing around the opening therein is a bearing rib 13 that is oval or half round in cross section 1n order to provide a convex bearing face.

Extending axially through the housing comprising the shell 10 and heads 11, is a tubular mandrel let having on its external surface a quick acting thread and portions of the mandrel adjacent to its ends bear in the bronze bushings 12. Those portions of the mandrel that project beyond the bushings are externally threaded in order that said mandrel at its upper end may be connected to the lower end of the drill tube T, and at its lower end to a sub or to the upper end of the body of a drill D1 Arranged on the interior of the housing of the underreamer, is a tapered or conical member 15, through which is formed an axially disposed threaded bore 16 that receives the threaded mandrel 14 and formed in the surface of this cone is a pair of oppositely disposed longitudinally extending slots 17 that are preferably T-shaped in cross section, although, if desired, these slots may be of ordinary dove-tail form.

Arranged to slide freely in the slots 17, are the T-shaped inner ends 18 of bits or cutter blades 19 of hardened metal, and which bits or cutter blades project horizontally outward through openings 20 thatare formed in the wall of shell 10. The outer vertical faces of these bits or cutter blades are preferably beveled slightly to form cutting edges 21 and, if desired, the outer portions of said bits may be notched to facilitate the cutting action and to permit the ready discharge of the cuttings from said bits.

Formed on the side faces of the bits 19 adjacent to their inner edges are vertically disposed ribs 22 that are adapted to bear directly against the inner face of the housing 10 when the bits or cutter blades are fully expanded and thus, in addition to the interlocking engagement between the inner portions of said bits and the conical member 15, said bits have a very firm and substantial bearing against the housing while they are in position for service.

In order to more effectually resist the strains and stresses that are impressed on the bits or cutter blades while the same are in service, the wall of housing 10 immediately adjacent to the openings 20 is reinforced by being appreciably increased in thickness and for the purpose of providing contact members or Wear receiving surfaces, longitudinally extending ribs 23 are formed on the external surface of the housing immediately adjacent to the sides of the openings 20 and these ribs extend the entire length of said housing.

These ribs, in addition to reinforcing the housing, function as contact members or wear receiving surfaces while the underreamer is being raised and lowered through the Well casing.

Formed on the ends of the conical member 15 immediately adjacent to the threaded bore 16, are bearing ribs 24 that are preferably half round in cross section and which are adapted to engage respectively with the bearing ribs 13 on the bronze bushings 12 when the conical member is at its upper or lower limit of movement.

By providing the bearing ribs 13 and 24 with rounded or convex bearing surfaces, the tendency of the ends of the conical member to freeze to the bronze bushings while in contact therewith is minimized and such tendency is further minimized by reason of the fact that the bushings 12 are formed of bronze and the conical member 15 is formed of metal such as cast steel.

Before the underreamer is lowered into the well, the threaded mandrel is rotated so as to effect a downward movement of the conical member 15 within the housing and due to the interengagement between the inner ends of the bits or cutter blades and the conical member 15, said bits or blades will be drawn inwardly through the openings 20 until the cutting edges of said bits or blades are practically flush with or slightly inset relative to the outer surfaces of the bearing ribs 23. The underreamer is now lowered into the casing and during this operation, the bearing ribs 23 function as guides to center the underreamer in the vasing and said ribs receive any wear that may result from contact between the underreamer housing and the casing.

WVhen the underreamer has been lowered to a point just below the lower end of the casing illustrated by dotted lines C in Fig. 1, the drill tube is rotated toward the right hand or clockwise and following such action, the conical member 15 Will be drawn upward through the housing 10 until its upper end bears against the bronze bushing at the top of said housing and, as this upward movement of the conical member takes place, the bits or cutter blades 19 will be positively expanded or moved outward to their limit of movement through the openings 20, or until the shoulders on ribs 22 bear against the inner surface of housing 10.

Thus said cutters are moved outward until their outer portions engage the wall of the drill hole below the lower end of the casing and, as the drill tube and underreamer con tinue to rotate, the well hole will be reamed or enlarged below the casing so as to enable the latter to be lowered into the well hole.

Inasmuch as the threaded mandrel 14 is tubular in form, circulation of water and soft mud may be effected in the usual manner through the drill tube and underreamer, and thus all cuttings from the underreamer are carried off with said circulation.

At the completion of the underreaming operations, the drill tube T is reversely rotated, or rotated toward the left hand, thus moving the conical member 15 from its position within the upper portion of the housing downwardly until the bearing rib 24 at the lower end bears against the corresponding bearing rib on the bushing at the lower end of the housing and such action effects a positive inward movement of the bits or cutter blades, so that the same are drawn into the housing and the underreamer may now be withdrawn from the well as the drill tube T is elevated therethrough.

In underreamers of the type to which my invention relates and where the ends of the bit actuating member make contact with the ends of the housing there is excessive wear between the ends of said bit actuating member and said housing and a decided advantage of my improved construction is the arrangement of the bushings 12 in the ends of the housing and the ribs on which bushings servc as bearings for the ends of the bit actuating member. By providing such bushings and mounting the same so that they may be readily removed from the ends of the housing it is possible to remove and replace these bushings from time to time when they become worn to such an extent as to render them unfit for service. Further, the removal and replacement of the bearing bushings 12 may be more readily accomplished by the rounded caps that are screw seated on the ends of the cylindrical housing 10.

Thus it will be seen that I have provided a relatively simple, practical and eflic'ient un- 1,ea2,21e

derreamer wherein the engagement of the bits or cutter blades with a conical member operating on a tubular threaded mandrel is ffective in positively expanding or moving said bits or cutter blades outwardly and liliewise for positively'withdrawing or movlng said bits or cutter blades into the-housing; and further, that the ends of the conical member that positively actuates the bits or cutter blades has direct positive bearing with the ends ofthe housing when the bits or cutter blades are expanded or withdrawn to their limits of movement and, further, that the bits or cutter blades are mounted in reinforced portions of the housing so that they are well able to withstand the strains and stresses that are'developed during cutting operations.

My improved underreamer is comparatively simple in construction, inexpensive of manufacture, may be readily assembled or taken apart, thereby facilitating inspection, repairs and replacements, and is very effective in performing the functions for which it is intended.

It will be understood that minor changes in the size, form and construction of the various parts of my improved underreamer may be made and substituted for those herein shown and described without departing from the spirit/of my invention, the scope of which is set forth in the appended claims.

I claim as my invention:

1. In an underreamer, a housing, caps removably seated on both ends of said housing, bushings seated in said caps, an externally threaded tubular mandrel extending axially through said housing and arranged for rotation in said bushings, a conical member arranged within the housing and mounted on said threaded mandrel and cutter blades arranged for movement through openings in the wall of the housing, the inner ends of which cutter blades are interengaged with said conical member.

2. In an underreamer, a housing, caps removably seated on both ends of said housing, bushings seated in said caps, an externally threaded tubular mandrel extending axially through said housing and arranged for rotation in said bushings, a conical member arranged within the'housing and mounted on said threaded mandrel, cutter blades arranged for movement through openings in the wall of the housing, the inner ends of which cutter blades are interengaged with said conical member, bearing ribs formed on said bushings and corresponding bearing ribs formed on the ends of said conical member.

3. In an underreamer, a housing, caps removably seated on the ends of said housing, which caps are provided with centrally arranged bearings, an externally threaded tubular mandrel extending axially through said housing and journaled for operation in the bearings in said caps, a conical member screw-seated in said mandrel within the housing, cutter blades arranged for o eration through openings in the wall of the ousing, the inner ends of which cutter blades are interengaged with said conical member and the wall of the housing around the openings through which said cutter blades operate being reinforced.

4. In an underreamer, a housing, caps removably seated on the ends of said housing, which caps are provided with centrally arranged bearings, an externally threaded tubular mandrel extending axially through said housing and journaled for operation in the bearings in said caps, a conical member screw-seated in said mandrel within the housing, cutter blades arranged for operation through openings in the Wall of the housing, the inner ends of which cutter blades are inter-engaged with said conical member, the wall of the housing around the openings through which said cutter blades operate being reinforced and longitudinally disposed bearing ribs formed on the outer surface of said housing.

' 5. In an underreamer, a housing comprising a hollow cylindrical body and separate heads removably on the ends thereof, bushings carried by said heads, an externally threaded tubular mandrel extending axially through said housing and arranged for rotation in said bushings, a conical member screwseated on said mandrel, cutter blades arranged for operation through openings in the wall of the housing and the inner ends of which cutter blades have sliding interengagement with said conical member.

6. In an underreamer, a housing comprising a hollow cylindrical body and separate heads removably on the ends thereof, bushings carried by said heads, an externally threaded tubular mandrel extending axially through said housing and arranged for rotation in said bushings, a conical member screw-seated on said mandrel, cutter blades arranged for operation through openings in the wall of the housing, the inner ends of which cutter blades have sliding interengagement with said conical member and reinforcing means formed on the wall of the housing adjacent to the openings through which said cutter blades operate.

7. In an underreamer, a housing, caps removably positioned on the ends of said housing and provided with centrally arranged bearings, an externally threaded tubular mandrel extending axially through said housing and arranged for rotation in said hearings in the ends of said housing, a conical member screw-seated on said mandrel within said housing, said conical member being provided with longitudinally disposed undercut slots, cutter blades arranged for operation through openings in the wall of the housing,

the inner ends of which cutter blades are provided with shouldered portions that occupy the undercut slots in said conical member, bushings in the ends of the housing which bushings function as bearings for the mandrel, bearing ribs formed on the inner faces of said bearings and bearing ribs formed on the ends of said conical member. v 8. In an underreamer, bushings in the ends 10 thereof, concentric bearing ribs formed on said bushings, an externally threaded tubular mandrel extending axially thru said housing and arranged for rotation in said'bush ings, bearin ribs on the ends of said mandrel, which earing ribs are adapted to engage the bearing ribs on the bushings, a tapered conical member screw-seated on said mandrel and cutter blades, the inner ends of which cutter blades have interengagement with said conical member, whereby said outter blades are positively moved radially relative to the axis of the mandrel as the conical member moves lengthwise thereon.

In testimony whereof I aflix my signature. EARL S. HARTSON. 

